Netflix’s Sandman portrays a very real sleeping illness — but does it get it right?

Humans inhabit the waking world, yet we spend a third of our lives sleeping, and, often, dreaming. We know there are definitely health risks associated with oversleeping. But what would happen if you simply went to bed one day and never woke up?

As it turns out, this farfetched premise might have a semblance of scientific truth — and it’s a key plot point in Netflix’s sci-fi fantasy epic, The Sandman, based on the Neil Gaiman comic book series.

In the show’s pilot episode, we’re introduced to Morpheus or the “Lord of Dreams,” who controls people’s slumbering visions. When he leaves his realm and travels to the waking world to reign in an out-of-control nightmare, an occultist captures him. While Morpheus is locked away for decades, people descend into a sleeping sickness known as “encephalitis lethargica.”

In a recent Twitter thread, writer Mark Sumner said the show’s illness is rooted in a real-life disease that afflicted millions a little more than a century ago. But just how true is the show’s depiction to the real-life illness — and can it actually teach us something about our current Covid-19 pandemic? Inverse spoke with scientific experts to unpack the sleepy science behind this strange, fascinating show.

Reel Science is an Inverse series that reveals the real (and fake) science behind your favorite movies and TV.

What is encephalitis lethargica?

Encephalitis lethargica is an epidemic that emerged in Vienna in late 1916, reported by a doctor named Constantin von Economo, who gave the new mysterious illness its name the following year. People of all ages were affected, but at least 50 percent were between 10 and 30 years old.

Leslie Hoffman, assistant professor of clinical anatomy, cell biology & physiology at Indiana University who co-authored an article in Brain on the disease, tells Inverse that the patients had “unusual neurological symptoms that did not fit with any known disease at the time.”

Encephalitis lethargica became epidemic in France, Austria, and England by 1918, then spread to the rest of Europe, North America, Central America, and India. It spread around the globe from 1917 to 1927, just as portrayed in The Sandman. Official data is sparse, but researchers think more than 1 million people contracted the disease, and more than 500,000 died from it. Estimates of mortality rates range from 20 to 40 percent — a shockingly high figure.

Unlike Sandman, in real life, we still don’t know what caused the disease. Some researchers suggest Spanish flu might be responsible, as patients presented with flu-like symptoms before they developed neurological problems.

“Encephalitis lethargica is thought to be caused by an autoimmune attack on different parts of the brain following infection by the Spanish flu,” Jamie Zeitzer, associate professor of psychiatry and behavioral sciences at Stanford University, tells Inverse. This is similar to Sydenham chorea, which occurs when neurological symptoms develop following rheumatic fever.

Scholars think the movement of soldiers during World War I helped spread the disease, which helps explain why encephalitis lethargica largely disappeared in the 1930s. There have been sporadic cases reported since, though Hoffman says these diagnoses may be unreliable because of “wide variability in diagnostic criteria.”

While the timing matches up, we can’t prove the connection between Spanish flu and encephalitis lethargica. Hoffman says there is evidence both for and against, and the rarity of new cases has made further investigation more difficult.

Is the “sleeping sickness” in the show accurate?

Morpheus gravely describes the sleeping sickness that has befallen nearly 1 million people in “in every city, town, and village in the world.” He says some “begged for sleep that would not come” while others sleepwalked. Many afflicted patients simply went to bed and never woke up.

That type of sleepy slumber might make for good family drama on TV, but it’s not completely accurate to the real-life epidemic, which more often caused lethargy and fatigue.

“I think the show overdramatized some of the symptoms of encephalitis lethargica,” Edward Shorter, a professor and Hannah Chair in the history of medicine at the University of Toronto who authored a paper on the disease, tells Inverse. “Its main characteristic was not a sleep you couldn’t wake up from, but crushing fatigue.”

The show largely oversimplifies a very complex disease. Zeitzer says Gaiman “merged several aspects of the disorder” in the comic. There were 28 officially reported forms of encephalitis lethargica, broken up into a few big subgroups.

In the first group, patients felt an “overwhelming desire to sleep” and could sleep for unusually long periods, but they could also easily be awakened, according to Hoffman.

Patients in the second group had insomnia and “remained rigid and immobile for long periods of time, but they could be easily moved by an external force,” Hoffman says. Although these patients were mentally present, their faces were often expressionless, perhaps appearing similar to the “perpetual sleepwalkers” seen in the show.

The third group was depicted in the 1990 film, Awakenings, in which Robin Williams plays a doctor treating patients who survived the epidemic. According to Hoffman, these “hyperkinetic” patients experienced repetitive muscle twitching, random movements of the face and limbs, and significant restlessness and fatigue — similar to Parkinson's.

“This form could fit with those described in the show who “begged for sleep that would not come,’ however insomnia is not one of the symptoms; in fact, many patients with the hyperkinetic form often experienced a reversal of day-night sleep cycles,” Hoffman says.

What can encephalitis lethargica teach us about Covid-19?

Several scholars have written papers in recent years comparing post-encephalitis lethargica patients to Covid long-haulers due to the presence of neurological issues in both cases — including chronic fatigue and brain fog — which may present for years after the initial infection.

Shorter says encephalitis lethargica patients may survive but develop a long-term neurological condition known as “postencephalitic Parkinsonism,” which refers to the abnormal movements and other neurological issues that patients in the movie Awakenings experienced. He calls encephalitis lethargica the “first psychiatric pandemic” due to its pronounced neurological symptoms.

“These postviral chronic syndromes seem to have the central nervous system in common, even though acutely they affect different organ systems,” Shorter says.

While encephalitis lethargica is now a largely forgotten ailment, its disease progression may hold lessons for current Covid-19 sufferers. One can only hope Covid-19 will eventually go the way of encephalitis lethargica.

“Encephalitis lethargica just went away,” Shorter says. “Maybe Covid will do the same.”

The Sandman is now streaming on Netflix.